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Showing 1-5 of 16 Abstracts search results

Document: 

SP142-05

Date: 

January 1, 1994

Author(s):

P. Soroushian and S. Marikunte

Publication:

Symposium Papers

Volume:

142

Abstract:

Relatively low-cost and energy-efficient materials with desirable short-term mechanical properties can be constructed using cellulose fibers as cement reinforcement. There are, however, concerns regarding the long-term performance of cellulose fiber reinforced cement composites; some cellulose fibers tend to disintegrate in the alkaline environment of cement. The growth of cement hydration products within the hollow cellulose fibers may also lead to excessive fiber-to-matrix bonding and brittle failure after exposure to natural weathering. This paper presents the results of an experimental study concerned with the long-term performance of cellulose fiber reinforced cement composites. Cellulose fiber reinforced cement composites were investigated, using accelerated weathering conditions representing repeated wetting and drying of materials in outside exposure conditions. The cement composites considered in this investigation incorporated 2 percent mass fractions of kraft pulp. Comprehensive replicated flexural test data were generated for various test ages at different wetting-drying cycles and were analyzed statistically. The analysis of variance and multiple comparison techniques were employed to derive reliable conclusions regarding the effect of accelerated wetting-drying cycles on flexural strength and toughness characteristics of cellulose fiber reinforced cement composites. The results generated in this study showed, at 95 percent level of confidence, that accelerated aging under repeated wetting-drying cycles had negligible effects on flexural strength, but led to reduced toughness and embrittlement of cellulose fiber reinforced cement composites.

DOI:

10.14359/1182


Document: 

SP142-10

Date: 

January 1, 1994

Author(s):

Sung-Woo Shin, Jung-Geun Oh, and S. K. Ghosh

Publication:

Symposium Papers

Volume:

142

Abstract:

Reports on an investigation on the behavior of high-strength concrete beams (with concrete compression strength equal to 11,600 psi or 80 MPa), with and without steel fiber reinforcement, to determine their diagonal cracking strength as well as nominal shear strength. Experimental data on the shear strength of steel fiber reinforced high-strength concrete beams are currently scarce to nonexistent. Twenty-two beam specimens were tested under monotonically increasing loads applied at midspan. The major test parameters included the volumetric ratio of steel fibers, the shear span-to-depth ratio, the amount of longitudinal reinforcement, and the amount of shear reinforcement. It was found that steel fiber reinforced high-strength concrete beams effectively resist abrupt shear failure. Such beams exhibit higher cracking loads and energy-absorption capabilities than comparable high-strength concrete beams without fibers. Empirical prediction equations are suggested for evaluating the diagonal cracking strength as well as nominal shear strength of steel fiber reinforced high-strength concrete beams.

DOI:

10.14359/3917


Document: 

SP142-12

Date: 

January 1, 1994

Author(s):

Lloyd E. Hackman, Mark B. Farrell, and Orville O. Dunham

Publication:

Symposium Papers

Volume:

142

Abstract:

An innovative technique for reinforcing concrete to achieve extremely high flexural strengths has been developed. This technique utilizes a steel fiber mat instead of short, discrete steel fibers. The mat configuration is preplaced for infiltration with a concrete slurry to yield a composite with flexural strengths approaching ten times that of conventional concrete. Applications include high-performance bridge decks, earthquake-resistant structures, nuclear waste containment, military applications, and other innovative uses in which flexural strength is at a premium. Stainless steel mats or other advanced alloys can be provided where corrosion resistance or high temperature strength are required.

DOI:

10.14359/1193


Document: 

SP142-13

Date: 

January 1, 1994

Author(s):

D. J. Stevens and D. Liu

Publication:

Symposium Papers

Volume:

142

Abstract:

It is well recognized that fiber reinforced concrete (FRC) exhibits a number of superior properties relative to plain concrete, such as improved strength, ductility, impact resistance, and failure toughness. These advantageous features of FRC can lead to novel structural applications, for which standard design and analysis procedures must be supplemented by numerical modeling (for example, the finite element method). This, in turn, makes necessary the development of satisfactory constitutive models that can predict the behavior of FRC under different load conditions, both monotonic and cyclic. In this paper, a constitutive model for FRC is developed loosely within the theory of mixtures. For plain concrete, an anisotropic, strain-based, continuum damage/plasticity model with kinematic and isotropic damage surfaces is developed. To represent the effect of the fibers, a simplified model that accounts for the tensile resistance of the fibers and the enhanced tensile resistance of the plain concrete is proposed. The predictions of the FRC constitutive model are compared to data from laboratory tests of steel fiber reinforced concrete (SFRC) specimens under uniaxial and biaxial loadings.

DOI:

10.14359/3963


Document: 

SP142-01

Date: 

January 1, 1994

Author(s):

S. P. Shah M. Sarigaphuti, and M. E. Karaguler

Publication:

Symposium Papers

Volume:

142

Abstract:

Concrete structures shrink when they are subjected to a drying environment. If this shrinkage is restrained, then tensile stresses develop and concrete may crack. One of the methods to reduce the adverse effects of shrinkage cracking is to reinforce concrete with short randomly distributed fibers. Another possible method is the use of wire mesh. The efficiency of fibers and wire mesh to arrest cracks in cementitious composites was studied. Different types of fibers (steel, polypropylene, and cellulose) with fiber content of 0.25 and 0.5 percent by volume of concrete were examined. Ring-type specimens were used for restrained shrinkage cracking tests. These fibers and wire mesh show significant reduction in crack width. Steel fiber reinforced concrete (0.5 percent addition) showed 80 percent reduction in maximum crack width and up to 90 percent reduction in average crack width. Concrete reinforced with 0.5 percent polypropylene or cellulose fibers was as effective as 0.25 percent steel fibers or wire mesh reinforced concrete (about 70 percent reduction in maximum and average crack width). Other properties, such as free (unrestrained) shrinkage and compressive strength were also investigated.

DOI:

10.14359/1178


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